The present invention concerns a dual-fuel fuel injector.
Publication DE 35 01 236 C1 discloses a cylinder cover for a piston internal combustion engine, wherein the cylinder cover has an injection nozzle in the center and at least two peripheral injection nozzles.
Gaseous fuels are gaining importance in the large engine sector, in particular in stationary engines for power generation. Because of its very good availability and more favorable emission potential compared with diesel fuel, natural gas is ideal for economic and environmentally-friendly engine operation. Most gas engines work on the spark-ignition combustion process, i.e. with homogeneous combustion and external ignition, wherein the ignition can be initiated either by a spark plug or by a diesel pilot injector. The spark-ignition combustion process has however the disadvantage that during the charge cycle, due to the external mixture formation, an undesirable methane loop occurs. Methane loops can however only be prevented if a combustion process with internal mixture formation is applied in the engine. For this, a direct high-pressure injection is required.
Dual-fuel nozzles, in particular those in which the gas valve and fuel needles are accommodated in the same nozzle body, are very complex to produce. The needles are e.g. arranged nested concentrically in each other in the nozzle body, see for example publication EP 1 274 933 B1, or housed separately in the nozzle body, e.g. the fuel needle is positioned centrally and further gas needles are arranged eccentrically in the nozzle body in order to cover the full combustion chamber range of 360°.
Irrespective of the variant concerned, the installation space in the nozzle body is always extremely constricted and hence disadvantageous for production of the nozzle in view of the necessary cost of production. This applies in particular if the gas shut-off elements (gas needles) must sit close to the combustion chamber at the nozzle holes, since otherwise a substantial proportion of gas continues to flow in or out after combustion and can adversely affect the hydrocarbon emissions.